Side effects Side effects of oral ED medicines are often mild. They’re often the first line of treatment for trouble getting or keeping an erection, called erectile dysfunction ED. If you prefer, you may contact the U. The medication was developed by U. If you are taking sildenafil to treat erectile dysfunction, follow your doctor’s directions and the guidelines in this paragraph. Required Documentation Mexican pharmacies offer prescription medications at lower prices than pharmacies in the United States.Is there an over-the-counter Viagra? Viagra is only available with a prescription in the United States, Canada, and most other countries. Viagra is sold under the generic name . Side Effects. Dizziness, headache, flushing, or stomach upset may occur. Vision changes such as increased sensitivity to light, blurred vision, or trouble telling blue and green colors apart may. It will be up to pharmacists to judge whether men over the age of 18 can safely be sold the little blue pills. Manufacturer Pfizer hopes to get stocks of Viagra Connect (sildenafil 50mg) into UK.